In Chapter 8, Dawkins discusses parental involvement. He explores the topic of having a favorite child. If a parent has limited parental investment they can give their children, then why divide it between offspring rather than devoting it all to one child to increase its chance of survival the most? This would not maximize her reproductive output. If all of her children have half of her genes, then she would be risking some of her genes by only investing in one child. By investing equally in all, she assures that all of her genes have a chance for survival. There are, however, excepts to the rule, like Dawkins points out. Sometimes there will be an offspring that is less fit than the rest, the runt per say. In this situation, it would be in the mothers best interest to reject the less fit child and distribute parental investment between the children most likely to survive. Additionally, in situations where a mother can only save one of her children, it would be in her best interest for her to save the child who is most likely to survive or the child who needs the least amount of parental care. For example, if she saves the older one, then she has more parental investment left to bear another child. On the other hand, if she helps the younger one who is weaker, they might both survive. At some point, the child itself benefits from leaving its mother and letting her spend her parental investment on other children. It’s all a game of energy cost in Dawkins’s opinion.
Dawkins also ponders on menopause in this chapter. He thinks it too is an Evolutionary Stable Strategy to conserve energy because at a certain age females are not as good at bearing children, making the attempt a waste of energy. This way, more parental investment in the form of caring can be allotted to grandchildren to increase their survival. Like Dawkins said before, rejecting a child who is less fit has benefits for the mother, and he views menopause as a way to reject a child before energy is even spent on conception.
Additionally, Dawkins contemplates what kin altruism for the selfish genes means for siblings. It would benefit a child to attain all of the attention from a parent, but it would hurt their siblings, who have 50% of their genes. Each situation is different, which is why you see some instances of a sibling being altruistic, like a younger sibling protecting a younger sibling, and some instances of siblings being selfish, like animal litters pushing the runt away from getting nutrients from the mother. In most cases, it is favorable for children to deceive in order to get more parental investment, but natural selection doesn’t favor selfishness because a selfish population does not survive, which does not favor the genes.